As is known, once molded, glass articles are extracted from the respective molds, are placed on top of a supporting surface known as a dead plate, and are then transferred onto a linear conveyor, which feeds them in a straight direction to a cooling station.
The glass articles are transferred from the dead plate to the linear conveyor by a transfer assembly, e.g. of the type described in the Applicant's European Patent Applications EP 1627850 B1 and EP 1627859 B1, which comprises a fixed support; a pusher with seats or compartments, for engaging a group of articles for transfer; and an articulated actuating arm connected to the fixed support at one end, and fitted with the pusher at the other.
The articulated arm comprises a powered first elongated portion hinged to the fixed support to rotate about a fixed hinge axis perpendicular to the dead plate; and a powered second elongated portion connected to the first elongated portion to rotate, with respect to the first elongated portion, about a movable hinge axis parallel to the fixed hinge axis.
In known solutions of the above type, when set to an engage position engaging the articles on the dead plate, the pusher projects from the arm, on the opposite side of the arm to the conveyor, and the movable hinge axis extends inside the space between two parallel planes perpendicular to the dead plate and respectively containing the straight travelling direction of the articles on the conveyor, and the fixed hinged axis; and the movable hinge axis remains inside this space as long as it takes to push or transfer the group of articles onto the conveyor.
As a result, when the articles are deposited on the conveyor, the centre of gravity of the group of articles transferred is located upstream, in the travelling direction of the articles on the conveyor, from a plane containing the fixed hinge axis and perpendicular to the travelling direction.
Because of the position of the movable hinge axis when pushing the articles onto the conveyor, and the resulting position of the centre of gravity of the articles on the conveyor, there is a limit to how fast the articles can be transferred, and therefore to how much the output rate can be increased, without damaging the articles and, above all, without some of the articles being left on the dead plate at the push stage, and others being hurled onto the conveyor at the release stage.
In other words, as the output rate and, therefore, the rotation speed of the arm about the fixed hinge axis increase, the articles in the group travel along even widely differing trajectories that get further and further apart radially, as shown in the FIG. 6 diagram, which shows trajectories of a group of three articles to be transferred, and the return trajectories of the articles. As shown in FIG. 6, depending on their locations on the dead plate, the articles travel along different trajectories, with different accelerations and different peripheral speeds, thus resulting, just before the articles are released onto the conveyor, in high speed and acceleration components perpendicular to the travelling direction of the articles on the conveyor.
FIG. 7 shows the speed curves of the articles at the push stage. As can be seen, the speed curves differ widely, but more important is the extent to which the speed of each article oscillates with respect to conveyor speed, especially close to the conveyor.